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May 14, 1963
3,090,018
D‘ W. FOSS
REFERENCE CAVITY RESONATOR
Filed Oct. 6, 1959
2 Sheets-Sheet l
INVENTOR.
DAVID
W. FOSS
BY
ATTORNE Y
May 14, 1963
D, w. Foss
3,090,018
REFERENCE CAVITY RESONATOR
Filed Oct. 6, 1959
2 Sheets-Sheet 2
INVENTOR.
DAVID W. FOSS
ATTORNEY
3,099,018
Patented May. 141, 1963
2
3,090,018
REFERENCE CAVITY RESONATOR
_
David W. Foss, Ipswich, Mass, assiguor, by mesne assign
ments, to ‘Varian Associates, Palo Alto, Calif., a cor
poration of California
Filed Oct. 6, 1959, Ser. No. 844,768
6 Claims. (Ql. 333--83)
pass around the reference cavity resonator unit after it is
inserted within the block 1 in the manner to be herein
after described. If desired the choke slots 10 and 11
may be also provided in the output face 7 to handle any
matching problems in the overall waveguide apparatus.
The replaceable reference cavity resonator unit 12 will
now be described with particular attention being directed
to FIG. 2. A main body cylinder 13, generally fabricated
from the metal commonly referred to as lnvar having
The present invention relates to electromagnetic wave
guide apparatus and more particularly to a novel struc 10 a low coe?icient of expansion, de?nes a resonant cavity 14
enclosed at opposite ends by cover members 15 and 16.
ture for mounting standard reference cavity resonators
A choke type plunger 17 is secured to cover member 16
in such apparatus.
by screws 18 and separated from 16 by spacers 44 of a
Reference cavities have achieved rwide usage in the
material having a high coe?icient of expansion thereby
microwave frequency spectrum to maintain a ?xed pre
determined precise reference frequency which can be 15 maintaining the frequency of the cavity resonator during
changes in ambient temperature. An external vane type
maintained under severe and variable environmental con
handle 19 is also secured to body cylinder 13 by means
ditions. Mobile transmitters or radar beacons may be
of screws 20 to provide for handling of the unit 12 in
regulated or activated accurately with such devices. An
the removal and insertion thereof within block \1.
example of prior art construction is illustrated in US.
A cylinder 21 extends from cover member 15 and
Patent No. 2,584,717 issued to D. Alpert et al. Such 20
houses a ?ne tuning mechanism for final adjustment of
resonators are generally manufactured as integral units
the resonant frequency of the cavity resonator after the
with the resonant cavity and mounting structure com
bined due to the necessity for control of frequency changes
tuning plunger 17 has been positioned.
Pins 22 pro
trude on opposite sides of cylinder 21 in a direction
25 perpendicular to the axis of cavity 14. Recessed dielec
taining the required frequency response.
tric covered windows 23 and 24 enclose opposed open
Often it becomes necessary to employ several resonators
ings in main body cylinder 13 to provide for transmission
having predetermined frequency settings and in such situ
of electromagnetic waves into and out of the cavity 14.
ations disassembling of the system is required in order
Mounting block v1 is provided with a key-way slot 25
to install another unit. This results in delays, increased
labor costs and lack of use of critical equipment. A need 30 in face 26 dimensioned to receive the end of the replace
able resonator 12 having the cylinder 21 and pins 22
has arisen, therefore, for an extremely precise, rapidly
with temperature variations as well as accuracy in main
replaceable structure to facilitate change of reference
frequencies within a short time and preferably without
disposed thereon. Metallic locking plate members 27
and 28 are disposed on either side of the arcuate portion
tools, in all types of waveguide systems with the same 35 of key-way 25 and secured to block 1 by means of screws
2?, 30, 35 and 36‘. The locking plate members are
qualities of performance under severe environmental con
provided with ramp angles 31 and 32 and grooves 33
ditions as exhibited by integrally combined resonators.
and 34. Screws 35 and 36 act as stop members. The
The present invention, therefore, has for its primary
positioning of the locking plate members will be noted
object the provision of a novel standard reference cavity
resonator having a separate, easily replaceable unit for 40 in FIGS. 3 and 4 with the stop members 35 and 36 dis
posed angularly to all the parallel Walls of block 1.
a microwave frequency waveguide apparatus to thereby
alter the frequency standard.
Another object is the provision of a novel reference
cavity resonator for use in microwave frequency wave
guide apparatus, the frequency thereof being readily
altered Without disassembling of the waveguide apparatus.
Further objects, features and advantages will be ap
parent after consideration of the following detailed speci
?cation and appended drawings, in which:
‘Ti
The installation of the replaceable cavity resonator unit
in block .1 will now be described reference being again
directed to FIGS. 3 and 4. A cavity resonator unit 12
set to the desired frequency is held by handle 19 in a
4.5 position with the windows 23 and 24 disposed approxi
mately 90° from the block openings 9. In this position,
pins 22 will enter key-way in the manner shown in
FIG. 3. Rotation of the unit will then result in pins 21
FIG. 1 is an exploded perspective view of an illustra 50 riding up ramps 31 and 32 and then dropping into grooves
33 and 34 against stop members 35 and 36 as shown in
tive embodiment;
FIG. 4. Within the cylindrical chamber de?ned by hol
FIG. 2 is a cross-sectional view along the line ‘2-“2 in
low block 1, two rubber 0 rings '37 and 38 are retained
FIG. 1;
*by two split washers of ?uorine polymer 39‘ and 40 set
FIG. 3 is an end view of the replaceable unit after
insertion in the mounting block; and
55 into counter bores in the chamber walls. The ridged
portion 45 of the main body cylinder 13 and the cover
FIG. 4 is an end view similar to FIG. 3 with the re
member 15 will bear against the washers and gradually
placeable unit rotated 90° to the locked position.
compress the 0 rings as the replaceable unit 12 is ro
Referring to the drawings, FIG. 1 is illustrative of the
tated to the locked position. The 0 rings and washers
preferred method of mounting the embodiment of the
invention in waveguide apparatus. A metallic mounting 60 provide not only the compressive force to retain the re
placeable unit in the locked position but also assure that
block 1 is secured between hollow pipe waveguide sec
the replaceable unit is concentrically disposed within
tions 2 and 3 by means of ?anges 4 and 5 abutting oppo
block 1 to prevent any frequency change due to misalign
site faces 6 and 7 of block 1 and screw fastening means
ment. The 0 rings also serve to buffer the effects of
introduced through ?ange holes 3. An opening ‘9 is
provided in opposite walls of block 1 mating with the 65 shock and vibration so that frequency change under such
conditions is negligible. In addition, these components
waveguide sections with the dimensions of the openings
are necessary to thermally isolate the Invar cylinder from
being approximately equal to the internal dimensions of
the
block member, commonly fabricated from aluminum.
the adjacent waveguide sections. Adjacent to the open
Since the two metallic members would result in cavity
ing 9 in the input face 6 of block 1, two slots 10 and 11
are provided parallel to the wide dimensions of the open 70 distortion; hence a frequency change with a change in
temperature. To eliminate the effect of humidity on the
ing. This arrangement provides a choke to suppress
resonant frequency the unit 12 is evacuated and ?lled with
transmitted off-resonance power that would otherwise
3,090,018
3
a gas at reduced pressure by means of exhaust tubulation
41 recessed ‘within handle 19.
Cover member 42‘ is se
cured to face 26 by means of screws 43 to enclose the
4
nator unit is rotated within said block member until said
grooves are engaged for aligning said pair of windows
with said openings in said block member to thereby posi~
cylinder 21 and locking plate members 27 and 28.
tively lock the resonator unit in the position to respond
The invention facilitates the use of any number of
replaceable units each pre-set to a different resonant
frequency. In actual installations, units have been in
to electromagnetic wave energy transmitted through the
serted and released as much as one hundred ?fty times
paired longitudinal slots are provided in at least one wall
while their frequencies have remained Within 0.20‘ mega
of the block member parallel to the longest dimension of
adjacent waveguide sections.
3. Waveguide apparatus according to claim 2 wherein
cycles of the original value. Over the temperature range 10 the openings adjacent to the waveguide sections.
of 75° C., the frequency change of all the units was less
4. Waveguide apparatus comprising a waveguide struc~
than 0.26 megacycles.
ture having ?rst pair of two aligned openings disposed
While an illustrative embodiment of the invention has
in opposite side walls of said waveguide structure, a refer
been speci?cally described, many variations or modi?ca~
ence cavity resonator unit having a pair of aligned Win
tions will occur to skilled artisans. It is my intention to 15 dows disposed in opposite side walls with the alignment
cover in the appended claims such variations 0r modi?
of said windows disposed transversely to the alignment
cations as fall within the spirit and scope of the invention.
of said openings, said resonator being removably
What is claimed is:
1. Waveguide apparatus comprising a metallic block
mounted within said ?rst pair of openings and the ends
of said unit protruding through said opening, twist lock
member adapted for mounting between hollow-pipe wave 20 means on said resonator unit and said waveguide struc
ture for locking said resonator to said waveguide struc
guide structure, said block member de?ning openings in
opposed walls to permit passage of electromagnetic wave
energy, a reference cavity resonator unit removably
mounted within said block member along an axis ex
ture with the alignment of said pair of windows coin
ciding with said waveguide alignment for preventing alter
ation of frequency response due to improper sealing and
tending perpendicular to the axis of the waveguide struc 25 alignment of said unit within said waveguide member.
ture, said resonator unit being responsive to a ?xed
5. The apparatus of claim 4 wherein said waveguide
predetermined resonant frequency and having a pair of
structure comprises a hollow block member with a second
pair of aligned openings disposed in opposite side walls
aligned ‘Windows, metallic means disposed on one wall of
and aligned perpendicular to said ?rst pair of openings,
said resonator unit for locking said resonator unit within
said block member with said pair of windows aligned with 30 means disposed on said block member for mounting a
pair of waveguide sections to communicate with said
said openings in said block member, and means disposed
second pair of aligned openings, and said pair of aligned
at one end of said resonator unit for engaging said lock
windows are aligned with said second pair of openings
ing means to prevent alteration of frequency response due
when said unit is locked within said block.
to improper seating of the resonator unit upon insertion
35
within said block member.
6. The apparatus of claim 4 wherein said twist lock
means comprises a cylindrical extension disposed on one
2. Waveguide apparatus comprising a metallic block
end of said unit and protrudes through one of said ?rst
member adapted for mounting between sections of hol
low-pipe waveguide, said block member de?ning openings
in opposed walls adjacent to said waveguide sections, said
block member further de?ning a cylindrical opening in
pair of openings, metallic pins extend laterally to the
axis of extension, a metallic member disposed around
said one opening and having incline ramp portions and
grooves, and resilient means disposes between said unit
one of the remaining walls and a key-way slot in the oppo
and said waveguide structure.
site wall, a reference cavity resonator unit adapted for
insertion and removal in said cylindrical opening with
References Cited in the ?le of this patent
an end thereof projecting through said key-way slot, said
UNITED STATES PATENTS
resonantor unit ‘being responsive to a ?xed predetermined 45
resonant frequency and having a pair of aligned windows,
2,451,982
Scott ________________ __ Oct. 19, 1948
metallic locking plate members disposed on opposed sides
of said key-way slot, each of said plate members de?ning
an inclined ramp portion and a groove, a cylindrical ex
tension disposed at one end of the resonator unit with 50
metallic pins extending laterally to the axis of the exten
sion, said pins engaging said ramp portions as said reso
2,734,174
2,781,500
2,783,295
2,791,720
2,817,760
2,831,047
HeinS _______________ __ Feb. 7, 1956
Armstrong ___________ __ Feb. 12, 1957
Ewing _______________ __ Feb. 26,
Lesch _______________ __ May 7,
Dobbertin ____________ __ Dec. 24,
Wadey ______________ __ Apr. 15,
1957
1957
1957
1958